I've talked a good bit about SVG's
<use></use> around here and using it to build an icon system. The beauty of
<use></use> is that you can reference just a part of some SVG defined elsewhere and draw just that part somewhere else. That ability allows you to build a whole system out of it, solving the "many images in one request, because that's super efficient" problem that we've solved in the past with CSS sprites and icon fonts.